Conventional robot devices operate to assemble and mate parts or a part and a tool automatically. Typically, alignment errors are not detected or corrected.
RCC devices, which are passively compliant, are available for assembly, mating and insertion tasks where it is desired to quickly and easily accommodate for relatively small misalignments. Three different types of RCC devices are disclosed in U.S. Pat. Nos. 4,098,001, 4,155,169, U.S. Pat. No. 4,337,579 and incorporated herein by reference. These devices have now been instrumented, U.S. Pat. No. 4,316,329, incorporated herein by reference, so that they are able to passively adjust to assemble misaligned parts and also indicate a measure of the misalignment.
Typically industrial robots are taught by introducing information into a robot data base such as by moving the robot through a sequence of operations and recording the various forces, velocities, and/or displacements that occur. Such information might also be obtained from external sources such as CAD or CAM data bases generated during design and manufacture of a product. If the input data is not entirely accurate or the environment of the robot or the robot itself has been altered then the robot has to be re-taught. Re-teaching may also be required because of shifts in the workpiece or work site, temperature drift, tolerance variations, aging, and other short and long term variable effects.
Various sensing schemes are used to attempt to monitor the robot's operation and reflect its interaction with its work environment. The sensor readings may eventually become data for robot operation but it may not be assumed that this data is completely accurate. It is customary and proper in control theory to assume rather that all sensor readings are corrupted by noise of various kinds which may result in wasted time and energy as well as unstable and possibly damaging behavior. Present sensing schemes do not provide for long-term accumulation of experience, tracking of drift, correction of teaching or alignment errors, etc.